The present invention relates to a composition containing a mixed silicate, a polysaccharide, and a crosslinked poly(2-acrylamido-2-methylpropanesulphonic acid) polymer, and the preparation and uses of the composition, in particular in the cosmetic field as a tightening agent, and for reducing and/or removing, and reducing and/or removing the appearance of, wrinkles and/or fine lines from the skin.
It is known to use clays and in particular mixed silicates, in cosmetic compositions. These silicates are known for their thixotropic properties and may be used as thickening, film-forming, emulsifying, adsorbent and/or absorbent agents. They are excellent gelling agents which are resistant to extreme pH and temperature conditions, and their fields of application, outside the cosmetic field, are vast (for example paints, agriculture, building products).
Patent WO-A-97/3 1619 describes cleansing and astringent cosmetic compositions containing, inter alia, laponite which belongs to the mixed silicate family and more particularly to the class of sodium and magnesium silicates. Laponites are synthetic stratified colloidal silicate used for their oil-absorbing properties. Such a laponite may be used as thickening and/or gelling agent in cosmetic compositions as described in Patent Application EP-A-412 449.
In addition, mixed silicates such as laponite are described as tightening agents in the document EP-A-1 008 340.
Unfortunately, compositions containing mixed silicates, most particularly when they are in the form of an emulsion (composition comprising at least one aqueous phase and t least one oily phase dispersed in one another) and when they contain more than 3% of mixed silicates, exhibit insufficient stability, which makes the incorporation of such a quantity of these silicates into cosmetic compositions difficult because the latter must have excellent stability during their entire commercial shelf life. The instability of emulsions containing more than 3% by weight of mixed silicates such as laponite occurs after a few days or even one to two weeks, and it manifests itself, inter alia, by a separation of the oily and aqueous phases, by a variation in color and/or in odor, and by a change in viscosity during the period of storage.
The document EP-A-1 008 340 describes the combination of laponite and xanthan gum. However, above 3% laponite, the composition containing this combination no longer has sufficient stability to constitute a commercially viable product.
The Inventors have discovered, surprisingly, that the combining of a polysaccharide and a polymer derived from 2-acrylamido-2-methylpropanesulphonic acid with one or more mixed silicates makes it possible to obtain compositions, including emulsions, having very good stability over time.